Here are a few pictures I got of the internet. Mine had a tan shell with large black spots that made it blend into it's surroundings. These are pictures of gorilla crabs.
http://i156.photobucket.com/albums/t...orillacrab.gif
http://i156.photobucket.com/albums/t...s/100_9133.jpg
I find new crabs all the time. Most of them have come in real small .You will usually notice them after they have grown bigger and easier to see.
Chris